Self-dispersing pigments

ABSTRACT

The disclosure provides self-dispersing pigment having an isoelectric point of at least about 8 comprising an inorganic particle, and in particular a titanium dioxide (TiO2) pigment, treated sequentially by: hydrolyzing an aluminum compound or basic aluminate to deposit a hydrous alumina surface; and adding a dual-functional compound comprising an anchoring group that attaches the dual-functional compound to the pigment surface, and a basic amine group comprising a primary, secondary or tertiary amine. These self-dispersing pigments are useful in making décor paper that may be used in paper laminates.

BACKGROUND OF THE DISCLOSURE

The present disclosure pertains to self-dispersing inorganic particles,and in particular to titanium dioxide pigments and their use in décorpaper and paper laminates made from such paper.

Paper laminates are in general well-known in the art, being suitable fora variety of uses including table and desk tops, countertops, wallpanels, floor surfacing and the like. Paper laminates have such a widevariety of uses because they can be made to be extremely durable, andcan be also made to resemble (both in appearance and texture) a widevariety of construction materials, including wood, stone, marble andtile, and they can be decorated to carry images and colors.

Typically, the paper laminates are made from décor paper by impregnatingthe paper with resins of various kinds, assembling several layers of oneor more types of laminate papers, and consolidating the assembly into aunitary core structure while converting the resin to a cured state. Thetype of resin and laminate paper used, and composition of the finalassembly, are generally dictated by the end use of the laminate.

Decorative paper laminates can be made by utilizing a decorated paperlayer as the visible paper layer in the unitary core structure. Theremainder of the core structure typically comprises various supportpaper layers, and may include one or more highly-opaque intermediatelayers between the decorative and support layers so that the appearanceof the support layers does not adversely impact the appearance ofdecorative layer.

Paper laminates may be produced by both low- and high-pressurelamination processes.

Décor papers typically comprise fillers such as titanium dioxide toincrease brightness and opacity to the paper. Typically, these fillersare incorporated into the fibrous paper web by wet end addition.

Often encountered in the décor paper making process are conditions wherethe pigment interacts with furnish components like wet strength resinand/or paper fibers in such a way that is detrimental to formation ofthe paper matrix. This negative interaction can be manifested as a lossin paper tensile strength (wet or dry), or a mottled appearance in thefinished sheet, or poor opacity. Thus a need exists for aself-dispersing pigment that exhibits improved compatibility withcomponents in the paper making furnish.

SUMMARY OF THE DISCLOSURE

In a first aspect, the disclosure provides a self-dispersing pigmenthaving an isoelectric point of at least about 8, more typically about 8to about 10, comprising an inorganic particle, more typically a titaniumdioxide (TiO₂) pigment, treated sequentially by:

(a) hydrolyzing an aluminum compound or basic aluminate to deposit ahydrous alumina surface; and

(b) adding a dual-functional compound comprising

-   -   i. an anchoring group that attaches the dual-functional compound        to the pigment surface, and    -   ii. a basic amine group comprising a primary, secondary or        tertiary amine.

In the first aspect, the disclosure provides a self-dispersing pigmentwherein the anchoring group is a carboxylic acid functional groupcomprising an acetate or salts thereof; a di-carboxylic acid groupcomprising malonate, succinate, glutarate, adipate or salts thereof; anoxoanion functional group comprising a phosphate, phosphonate, sulfate,or sulfonate; or a substituted 1,3-diketone or a substituted3-ketoamide.

In the first aspect, the disclosure provides a self-dispersing pigmentwherein the basic amine group is ammine; N-methyl, ethyl, propyl, butyl,cyclopentyl, or cyclohexylamine; or N,N-dimethyl, diethyl, dipropyl,dibutyl, dicyclopentyl, dicyclohexyl amine or mixed dialkylamines suchas N,N-methylethyl, etc. More typically utilized amine groups compriseammine (—NH₂), N-methyl amine, or N,N-dimethyl amine.

In the first aspect, the disclosure provides a self-dispersing pigmentfurther comprising a tethering group that chemically connects theanchoring group to the basic amine group, wherein the tethering groupcomprises:

-   -   (a) an alkyl chain of 1-8 carbon atoms; more typically 1-4        carbon atoms;    -   (b) a polyetheramine comprising poly(oxyethylene) or        poly(oxypropylene), or mixtures thereof, whereby the weight        average molecular weight of the tether is about 220 to about        2000; e.g. Jeffamine® D, ED, and EDR series; or    -   (c) a carbon, oxygen, nitrogen, phosphorous, or sulfur atom at        the attachment point to the anchoring group.

In the first aspect, the disclosure provides a self-dispersing pigmentwherein the dual functional compound comprises alpha-omega aminoacidssuch as beta-alanine, gamma-aminobutyric acid, and epsilon-aminocaproicacid; alpha-amino acids such as lysine, argenine, aspartic acid or saltsthereof.

In the first aspect, the disclosure provides a self-dispersing pigmentwherein the dual-functional compound comprises:

(i) an aminomalonate derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group as described above;

R′ and R″ are each individually selected from hydrogen, alkyl,cycloalkyl, alkyl-aryl, alkenyl, cycloalkenyl, alkene, alkylene,arylene, alkylarylene, arylalkylene or cycloalkylene;

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene;and

n=0-50;

(ii) an aminosuccinate derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group as described above;

R′ and R″ are each individually selected from hydrogen, alkyl,cycloalkyl, alkyl-aryl, alkenyl, cycloalkenyl, alkene, alkylene,arylene, alkylarylene, arylalkylene or cycloalkylene;

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene;and

n=0-50;

(iii) a 2,4-pentandione derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group as described above;

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, and cycloalkylene;and

n=0-50; or

(iv) a 3-ketobutanamide derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, and cycloalkylene.

In the first aspect, the disclosure provides a self-dispersing pigmentwherein X comprises methylene, oxyethane, or oxypropane groups whereinn=0 to 50; or polyetheramine co-polymers comprising both oxoethylene andoxopropylene monomers.

In the first aspect, the disclosure provides slurry comprising aself-dispersing pigment comprising pigment solids of 10% and having a pHof the pigment slurry less than about 7, more typically about 5 to about7.

In the first aspect, the disclosure provides a self-dispersing pigmenthaving a surface area of at least 15 m²/g.

In a second aspect, the disclosure provides a process for preparing aself-dispersing pigment comprising

(a) adding a dual functional compound with an acidic aluminum salt toform an aqueous solution, wherein the dual functional compoundcomprises:

i an anchoring group that attaches the dual-functional compound to thepigment surface, and

ii a basic amine group comprising a primary, secondary or tertiaryamine;

(b) adding a base to the mixture from step (a) whereby the pH is raisedto about 4 to about 9 to form a turbid solution; and

(c) adding the mixture from step (b) to a slurry of inorganic particles,in particular TiO₂ pigment particles whereby a hydrous alumina and thedual functional compound comprise a surface treatment.

In the second aspect, the disclosure provides a process for preparing aself-dispersing pigment wherein the acidic aluminum salt comprisesaluminum sulfate hydrate, aluminum chloride hydrate, or aluminum nitratehydrate and wherein the base comprises sodium hydroxide, sodiumcarbonate, or ammonium hydroxide.

By “self-dispersing pigment” we mean a pigment with an attribute that isachieved when the pigment zeta potential becomes a dominant forcekeeping pigment particles separated, i.e., dispersed in the aqueousphase. This force may be strong enough to separate weakly agglomeratedpigment particles when suspended in an aqueous medium under low shearconditions. Since the zeta potential varies as a function of solution pHand ionic strength, ideally pigment particles maintain sufficientlike-charge providing a repulsive force thereby keeping the particlesseparated and suspended.

DETAILED DESCRIPTION OF THE DISCLOSURE

In this disclosure “comprising” is to be interpreted as specifying thepresence of the stated features, integers, steps, or components asreferred to, but does not preclude the presence or addition of one ormore features, integers, steps, or components, or groups thereof.Additionally, the term “comprising” is intended to include examplesencompassed by the terms “consisting essentially of” and “consistingof.” Similarly, the term “consisting essentially of” is intended toinclude examples encompassed by the term “consisting of.”

In this disclosure, when an amount, concentration, or other value orparameter is given as either a range, typical range, or a list of uppertypical values and lower typical values, this is to be understood asspecifically disclosing all ranges formed from any pair of any upperrange limit or typical value and any lower range limit or typical value,regardless of whether ranges are separately disclosed. Where a range ofnumerical values is recited herein, unless otherwise stated, the rangeis intended to include the endpoints thereof, and all integers andfractions within the range. It is not intended that the scope of thedisclosure be limited to the specific values recited when defining arange.

In this disclosure, terms in the singular and the singular forms “a,”“an,” and “the,” for example, include plural referents unless thecontent clearly dictates otherwise. Thus, for example, reference to“TiO₂ particle”, “the TiO₂ particle”, or “a TiO₂ particle” also includesa plurality of TiO₂ particles.

Inorganic Particle:

The inorganic particle is typically an inorganic metal oxide or mixedmetal oxide pigment particle, more typically a titanium dioxide particlethat may be a pigment or a nanoparticle, wherein the inorganic particle,typically inorganic metal oxide or mixed metal oxide particle, moretypically titanium dioxide particle provides enhanced compatibility in adécor paper furnish. By inorganic particle it is meant an inorganicparticulate material that becomes dispersed throughout a final productsuch as a décor paper composition and imparts color and opacity to it.Some examples of inorganic particles include but are not limited to ZnO,TiO₂, SrTiO₃, BaSO₄, PbCO₃, BaTiO₃, Ce₂O₃, Al₂O₃, CaCO₃ and ZrO₂.

Titanium Dioxide Pigment:

Titanium dioxide (TiO₂) pigment useful in the present disclosure may bein the rutile or anatase crystalline form, with the rutile form beingtypical. It is commonly made by either a chloride process or a sulfateprocess. In the chloride process, TiCl₄ is oxidized to TiO₂ particles.In the sulfate process, sulfuric acid and ore containing titanium aredissolved, and the resulting solution goes through a series of steps toyield TiO₂. Both the sulfate and chloride processes are described ingreater detail in “The Pigment Handbook”, Vol. 1, 2nd Ed., John Wiley &Sons, NY (1988), the relevant teachings of which are incorporated hereinby reference for all purposes as if fully set forth.

By “pigment” it is meant that the titanium dioxide particles have anaverage size of less than about 1 micron. Typically, the particles havean average size of from about 0.020 to about 0.95 microns, moretypically from about 0.050 to about 0.75 microns, and most typicallyfrom about 0.075 to about 0.50 microns. Also typical are pigments with aspecific gravity in the range of about 3.5 to about 6 g/cc.

The untreated titanium dioxide pigment may be surface treated. By“surface treated” it is meant titanium dioxide pigment particles havebeen contacted with the compounds described herein wherein the compoundsare adsorbed on the surface of the titanium dioxide particle, or areaction product of at least one of the compounds with the titaniumdioxide particle is present on the surface as an adsorbed species orchemically bonded to the surface. The compounds or their reactionproducts or combination thereof may be present as a treatment, inparticular a coating, either single layer or double layer, continuous ornon-continuous, on the surface of the pigment.

For example, the titanium dioxide particle, typically a pigmentparticle, may bear one or more surface treatments. The outermosttreatment may be obtained by sequentially

(a) hydrolyzing an aluminum compound or basic aluminate to deposit ahydrous alumina surface; and

(b) adding a dual-functional compound comprising:

-   -   (i) an anchoring group that attaches the dual-functional        compound to the pigment surface, and    -   (ii) a basic amine group comprising a primary, secondary or        tertiary amine.

The aluminum compound or basic aluminate results in an hydrous aluminatreatment on the surface, typically the outermost surface, of thetitanium dioxide particle and it is present in the amount of at leastabout 3% of alumina, more typically about 4.5 to about 7%, based on thetotal weight of the treated titanium dioxide particle. Some suitablealuminum compounds and basic aluminates include aluminum sulfatehydrate, aluminum chloride hydrate, or aluminum nitrate hydrate andalkali aluminates, and more typically sodium or potassium aluminate.

The dual-functional compound comprises an anchoring group that attachesthe dual-functional compound to the pigment surface, typically theoutermost surface, and a basic amine group comprising a primary,secondary or tertiary amine. The anchoring group may be a carboxylicacid functional group comprising an acetate or salts thereof; adi-carboxylic acid group comprising malonate, succinate, glutarate,adipate or salts thereof; an oxoanion functional group comprising aphosphate, phosphonate, sulfate, or sulfonate; or a diketone such as aC3 substituted 2,4-pentanedione or a substituted 3-ketobutanamidederivative. The dual functional compound is present in an amount of lessthan 10% by weight, based on the weight of treated pigment, moretypically about 0.4% to about 3%, based on the weight of treatedpigment.

Substituents on the basic amine group are selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl,alkene, alkylene, or cycloalkylene, more typically short chain alkylscomprising methyl, ethyl, or propyl, and still more typically ammine.

The dual functional compound may comprise alpha-omega aminoacids such asbeta-alanine, gamma-aminobutyric acid, and epsilon-aminocaproic acid;alpha-amino acids such as lysine, argenine, aspartic acid or saltsthereof.

Alternately, the dual-functional compound comprises an aminomalonatederivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group;

R′ and R″ are each individually selected from hydrogen, alkyl,cycloalkyl, alkyl-aryl, alkenyl, cycloalkenyl, alkene, alkylene,arylene, alkylarylene, arylalkylene or cycloalkylene; more typicallyhydrogen, alkyl of 1 to 8 carbon atoms, aryl of 6 to 8 carbon atoms, andstill more typical where R′ and R″ are selected from hydrogen, methyl,or ethyl.

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene,more typically short chain alkyls comprising methyl, ethyl, or propyl,and still more typically ammine; and

n=0-50.

Typically, when X is methylene, n=1-8, and more typically n=1-4. When Xis oxymethylene or oxypropylene, n ranges from 2.5 to 50, more typically6-18. Some examples of aminomalonate derivatives include methyl andethyl esters of 2-(2-aminoethyl)malonic acid, more typically2-(2-aminoethyl)dimethylmalonate.

The dual functional compound may alternately comprise an aminosuccinatederivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group and

R′ and R″ are each individually selected from hydrogen, alkyl,cycloalkyl, alkyl-aryl, alkenyl, cycloalkenyl, alkene, alkylene,arylene, alkylarylene, arylalkylene or cycloalkylene; more typicallyhydrogen, alkyl of 1 to 8 carbon atoms, aryl of 6 to 8 carbon atoms, andstill more typically where R′ and R″ are hydrogen, methyl, or ethyl.

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene,more typically short chain alkyls comprising methyl, ethyl, or propyl,and still more typically ammine;

and

n=0-50.

Typically, when X is methylene, n=1-8, and more typically n=1-4. When Xis oxymethylene or oxypropylene, n ranges from 2.5 to 50, more typically6-18. Some examples of aminosuccinate derivatives include the methyl andethyl esters of N-substituted aspartic acid, more typicallyN-(2-aminoethyl)aspartic acid.

The dual functional compound may alternately comprise an acetoacetatederivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group and

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene,more typically short chain alkyls comprising methyl, ethyl, or propyl,and still more typically ammine;

and

n=0-50.

Typically, when X is methylene, n=1-8, and more typically n=1-4. When Xis oxymethylene or oxypropylene, n ranges from 2.5 to 50, more typically6-18. An example of an acetoacetate derivative is3-(2-aminoethyl)-2,4-pentanedione.

The dual functional compound may alternately comprise a 3-ketoamide(amidoacetate) derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group and

R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene,more typically short chain alkyls comprising methyl, ethyl, or propyl,and still more typically ammine;

and

n=0-50.

Typically, when X is methylene, n=1-8, and more typically n=1-4. When Xis oxymethylene or oxypropylene, n ranges from 2.5 to 50, more typically6-18. Some examples of amidoacetate derivatives include theethylenediamine and diethylenetriamine amides, more typicallyN-(2-aminoethyl)-3-oxo-butanamide.

Since the tendency to raise the pigment IEP is proportional to theamount of amine functionality imparted to the pigment surface, it isappropriate to express the molar amount of dual functional compoundadded to 100 g of treated pigment as the millimolar % of N-added. Forexample, amounts of dual functional compound used to effectively raisepigment IEP ranged from 2 mmole % to 10 mmole %, more typically 4 mmole% to 8 mmole %. Thus for typical, low molecular weight, dual functionalcompound beta-alanine, a dosage of 5 mmole % translates into 0.45 weight%. In contrast, in a high molecular weight example, the JeffamineED-2003 (m.w.˜2000) adduct of 3-ketobutanamide, requires 10.4 weight %to deliver 5 mmole % amine equivalents.

The dual functional compound further comprises a tethering group thatchemically connects the anchoring group to the basic amine group,wherein the tethering group comprises,

-   -   (a) an alkyl group of 1-8 carbon atoms; more typically 1-4        carbon atoms;    -   (b) a polyetheramine comprising poly(oxyethylene) or        poly(oxypropylene), or mixtures thereof, whereby the weight        average molecular weight of the tethering group is about 220 to        about 2000. Some examples of (b) include Jeffamine® D, ED, and        EDR series

A carbon, oxygen, nitrogen, phosphorous, or sulfur atom can be at theattachment point from the tether to the anchoring group.

In one specific embodiment, in the dual functional compound used toprepare the self-dispersing pigment, X comprises methylene, oxyethane,or oxypropane groups, wherein n=0 to 50; or polyetheramine co-polymerscomprising both oxoethylene and oxopropylene monomers.

In slurries made using the self-dispersing pigment, the pigment solidscomprise at least about 10%, more typically 35% and the pH of thepigment slurry is less than about 7, more typically about 5 to about 7.The self-dispersing pigment has surface area at least 15 m²/g, moretypically 25-35 m²/g.

Alternately, the treated inorganic particle, in particular a titaniumdioxide particle, may comprise at least one further oxide treatment, forexample silica, alumina, zirconia or ceria, aluminosilicate oraluminophosphate. This alternate treatment may be present in the amountof the amount about 0.1 wt % to about 20 wt %, typically from about 0.5wt % to about 5 wt %, and more typically from about 0.5 wt % to about1.5 wt %, based on the total weight of the treated titanium dioxideparticle. The treatment may be applied by methods known to one skilledin the art. A typical method of adding a silica treatment to the TiO₂particle is by wet treatment similar to that disclosed in U.S. Pat. No.5,993,533. An alternate method of adding a silica treatment to the TiO₂particle is by deposition of pyrogenic silica onto a pyrogenic titaniumdioxide particle, as described in U.S. Pat. No. 5,992,120, or byco-oxygenation of silicon tetrachloride with titanium tetrachloride, asdescribed in U.S. Pat. Nos. 5,562,764, and 7,029,648 which areincorporated herein by reference. Other pyrogenically-deposited metaloxide treatments include the use of doped aluminum alloys that result inthe generation of a volatile metal chloride that is subsequentlyoxidized and deposited on the pigment particle surface in the gas phase.Co-oxygenation of the metal chloride species yields the correspondingmetal oxide. Thus using a silicon-aluminum or a tungsten-aluminum alloyresulted in deposition of the corresponding silica and tungsten oxides,respectively. Patent Publications WO2011/059938A1 and WO2012/039730A1describe these procedures in greater detail and are incorporated hereinby reference.

Typically, the oxide treatment provided may be in two layers wherein thefirst layer comprises at least about 3.0% of alumina, more typicallyabout 5.5 to about 6%, based on the total weight of the treated titaniumdioxide particle, and at least about 1% of phosphorous pentoxide, P₂O₅,more typically about 1.5% to about 3.0% of phosphorous pentoxide, P₂O₅,based on the total weight of the treated titanium dioxide particle. In aspecific embodiment, the second layer of oxide on the titanium dioxidepigment comprises silica present in the amount of at least about 1.5%,more typically about 6 to about 14%, and still more typically about 9.5to about 12%, based on the total weight of the treated titanium dioxideparticle.

The titanium dioxide pigment that is to be surface treated may also bearone or more metal oxide and/or phosphated surface treatments, such asdisclosed in U.S. Pat. Nos. 4,461,810, 4,737,194 and WO2004/061013 (thedisclosures of which are incorporated by reference herein. Thesecoatings may be applied using techniques known by those skilled in theart.

Typical are the phosphated metal oxide coated titanium dioxide pigments,such as the phosphated alumina and phosphated alumina/ceria oxide coatedvarieties.

Examples of suitable commercially available titanium dioxide pigmentsinclude alumina-coated titanium dioxide pigments such as R700 and R706(available from E. I. duPont de Nemours and Company, Wilmington Del.),alumina/phosphate coated titanium-dioxide pigments such as R796+(available from E. I. duPont de Nemours and Company, Wilmington Del.);and alumina/phosphate/ceria coated titanium-dioxide pigments such asR794 (available from E. I. duPont de Nemours and Company, WilmingtonDel.).

Process for Preparing Treated Titanium Dioxide Particles

The process for preparing a self-dispersing pigment comprises:

(a) adding a dual functional compound with an acidic aluminum salt toform an aqueous solution, wherein the dual functional compoundcomprises:

i an anchoring group that attaches the dual-functional compound to thepigment surface, and

ii a basic amine group comprising a primary, secondary or tertiaryamine;

(b) adding a base to the mixture from step (a) whereby the pH is raisedto about 4 to about 9 to form a turbid solution; and

(c) adding the mixture from step (b) to a slurry of inorganic particles,in particular a TiO₂ pigment, whereby a hydrous alumina treatment andthe dual functional compound are deposited on the pigment surface.

The acidic aluminum salt comprises aluminium sulfate hydrate, oraluminum nitrate hydrate, more typically aluminum chloride hydrate, andwherein the base comprises sodium hydroxide, sodium carbonate, or moretypically ammonium hydroxide. Starting with the chosen amount of dualfunctional compound to give the desired pigment IEP, the accompanyingamount of acidic aluminum salt is chosen such that the molar ratio ofdual functional compound to Al is <3, more typically about 1 to about2.5. In this manner a mixture more prone to hydrolysis and ensuingdeposition is used to augment the pigment surface. Less desirable hereare the aluminum complexes of bidentate ligands such as the anion ofacetylacetone (i.e. 2,4-pentanedione). Such complexes are well-knownfrom the coordination chemistry literature, with thetris(acetylacetonato)aluminum complex known for its stability (boilingpoint of 314° C.) and non-polar nature, being insoluble in water.

The titanium dioxide particle can be surface treated in any number ofways well-known to those of ordinary skill in the relevant art, asexemplified by the previously incorporated references mentioned above.For example, the treatments can be applied by injector treatment,addition to a micronizer, or by simple blending with a slurry of thetitanium dioxide.

The surface-modified titanium dioxide can be dispersed in water at aconcentration of below about 10 weight percent, based on the entireweight of the dispersion, typically about 3 to about 5 weight percentusing any suitable technique known in the art. An example of a suitabledispersion technique is sonication. The surface-modified titaniumdioxide of this disclosure is cationic. The isoelectric point,determined by the pH value when the zeta potential has a value of zero,of the surface-modified titanium dioxide of this disclosure has anisoelectric point greater than 8, typically greater than 9, even moretypically in the range of about 9 to about 10. The isoelectric point canbe determined using the zeta potential measurement procedure describedin the Examples set forth herein below. The amount of deposited dualfunctional compound allows control of the isoelectric point of at least8.0, more typically between 8.0 and 9.0, which can be beneficial infacilitating the dispersion and/or flocculation of the particulatecompositions during plant processing and décor paper production. Havinga high IEP means that the pigment particle possesses a cationic chargeunder conditions when the pigment is introduced into the décor paperfurnish. The cationic pigment surface, possessing sufficient charge atpH<7, is more likely to interact with the negatively charged paperfibers and less likely to adsorb cationic wet strength resin.

Typically, the particle to particle surface treatments are substantiallyhomogenous. By this we mean that each core particle has attached to itssurface an amount of alumina or aluminophosphate such that thevariability in alumina and phosphate levels among particles is so low asto make all particles interact with water, organic solvent or dispersantmolecules in the same manner (that is, all particles interact with theirchemical environment in a common manner and to a common extent).Typically, the treated titanium dioxide particles are completelydispersed in water to form a slurry in less than 10 minutes, moretypically less than about 5 minutes. By “completely dispersed” we meanthat the dispersion is composed of individual particles or small groupsof particles created during the particle formation stage (hardaggregates) and that all soft agglomerates have been reduced toindividual particles.

After treatment according to this process the pigment is recovered byknown procedures including neutralization of the slurry and ifnecessary, filtration, washing, drying and frequently a dry grindingstep such as micronizing. Drying is not necessary, however, as a slurryof the product can be used directly in preparing paper dispersions wherewater is the liquid phase.

Applications

The treated titanium dioxide particles may be used in paper laminates.The paper laminates of this disclosure are useful as flooring,furniture, countertops, artificial wood surface, and artificial stonesurface.

Décor Paper

Décor paper may contain fillers such as treated titanium dioxideprepared as described above and also additional fillers. Some examplesof other fillers include talcum, zinc oxide, kaolin, calcium carbonateand mixtures thereof.

The filler component of the decorative paper can be about 10 to about65% by weight, in particular about 30 to about 45% by weight, based onthe total weight of the décor paper. The basis weight of the décor paperbase can be in the range of about 30 to about 300 g/m², and inparticular about 90 to about 110 g/m². The basis weights are selected asa function of the particular application.

To form a paper sheet, the titanium dioxide suspension can be mixed withpulp, for example refined wood pulp such as eucalyptus pulp, in anaqueous dispersion. The pH of the pulp dispersion is typically about 6to about 8, more typically about 7 to about 7.5. The pulp dispersion canbe used to form paper by conventional techniques.

Coniferous wood pulps (long fiber pulps) or hardwood pulps such aseucalyptus (short fibered pulps) and mixtures thereof are useful aspulps in the manufacture of décor paper base. It is also possible to usecotton fibers or mixtures all these types of pulps. A mixture ofconiferous wood and hardwood pulps in a ratio of about 10:90 to about90:10, and in particular about 30:70 to about 70:30 can be useful. Thepulp can have a degree of beating of 20° to about 60° SR according toSchopper-Riegler.

The décor paper may also contain a cationic polymer that may comprise anepichlorohydrin and tertiary amine or a quaternary ammonium compoundsuch as chlorohydroxypropyl trimethyl ammonium chloride or glycidyltrimethyl ammonium chloride. Most typically the cationic polymer is aquaternary ammonium compound. Cationic polymers such as wet strengthenhancing agents that include polyamide/polyamine epichlorohydrinresins, other polyamine derivatives or polyamide derivatives, cationicpolyacrylates, modified melamine formaldehyde resins or cationizedstarches are also useful and can be added to form the dispersion. Otherresins include, for example, diallyl phthalates, epoxide resins, ureaformaldehyde resins, urea-acrylic acid ester copolyesters, melamineformaldehyde resins, melamine phenol formaldehyde resins, phenolformaldehyde resins, poly(meth)acrylates and/or unsaturated polyesterresins. The cationic polymer is present in the amount of about 0.5 toabout 1.5%, based on the dry polymer weight to the total dry weight pulpfibers used in the paper.

Retention aids, wet-strength, retention, sizing (internal and surface)and fixing agents and other substances such as organic and inorganiccolored pigments, dyes, optical brighteners and dispersants may also beuseful in forming the dispersions and may also be added as required toachieve the desired end properties of the paper. Retention aids areadded in order to minimize losses of titanium dioxide and other finecomponents during the papermaking process, which adds cost, as do theuse of other additives such as wet-strength agents.

Examples of papers used in paper laminates may be found in U.S. Pat. No.6,599,592 (the disclosure of which is incorporated by reference hereinfor all purposes as if fully set forth) and the above-incorporatedreferences, including but not limited to U.S. Pat. Nos. 5,679,219,6,706,372 and 6,783,631.

As indicated above, the paper typically comprises a number of componentsincluding, for example, various pigments, retention agents andwet-strength agents. The pigments, for example, impart desiredproperties such as opacity and whiteness to the final paper, and acommonly used pigment is titanium dioxide.

The treated titanium dioxide particle can be used to prepare the décorpaper in any of the customary ways, wherein at least a portion, andtypically all of the titanium dioxide pigment typically used in suchpapermaking is replaced with the treated titanium dioxide pigment.

As indicated above, the décor paper in accordance with the presentdisclosure is an opaque, cellulose pulp-based sheet containing atitanium dioxide pigment component in an amount of about 45 wt % orless, more typically from about 10 wt % to about 45 wt %, and still moretypically from about 25 wt % to about 42 wt %, wherein the titaniumdioxide pigment component comprises the all or some of the treatedtitanium dioxide particle of this disclosure. In one typical embodiment,the treated titanium dioxide pigment component comprises at least about25 wt %, and more typically at least about 40 wt % (based on the weightof the titanium dioxide pigment component) of the treated titaniumdioxide pigment of this disclosure. In another typical embodiment, thetitanium dioxide pigment component consists essentially of the treatedtitanium dioxide pigment of this disclosure. In yet another typicalembodiment, the titanium dioxide pigment component comprisessubstantially only the treated titanium dioxide pigment of thisdisclosure.

Paper Laminates

Paper laminates in accordance with the present disclosure can be made byany of the conventional processes well known to those of ordinary skillin the relevant art, as described in many of the previously incorporatedreferences.

Typically, the process of making paper laminates begins with rawmaterials—impregnating resins such as phenolic and melamine resins,brown paper (such as kraft paper) and high-grade print paper (a laminatepaper in accordance with the present disclosure).

The brown paper serves as a carrier for the impregnating resins, andlends reinforcing strength and thickness to the finished laminate. Thehigh-grade paper is the decorative sheet, for example, a solid color, aprinted pattern or a printed wood grain.

In an industrial-scale process, rolls of paper are typically loaded on aspindle at the “wet end” of a resin treater for impregnation with aresin. The high-grade (decorative) surface papers are treated with aclear resin, such as melamine resin, so as to not affect the surface(decorative) appearance of the paper. Since appearance is not criticalfor the brown paper, it may be treated with a colored resin such asphenolic resin.

Two methods are commonly used to impregnate the paper with resin. Theusual way (and the fastest and most efficient) is called “reverse-rollcoating.” In this process, the paper is drawn between two big rollers,one of which applies a thin coating of resin to one side of the paper.This thin coating is given time to soak through the paper as it passesthrough to a drying oven. Almost all of the brown paper is treated bythe reverse-roll process, because it is more efficient and permits fullcoating with less resin and waste.

Another way is a “dip and squeeze” process, in which the paper is drawnthrough a vat of resin, and then passed through rollers that squeeze offexcess resin. The surface (decorative) papers are usually resin isimpregnated by the dip-and-squeeze process because, although slower, itpermits a heavier coating of the impregnating resin for improvingsurface properties in the final laminate, such as durability andresistance to stains and heat.

After being impregnated with resin, the paper (as a continuous sheet) ispassed through a drying (treater) oven to the “dry end,” where it is cutinto sheets.

The resin-impregnated paper should have a consistent thickness to avoidunevenness in the finished laminate.

In the assembly of the laminate components, the top is generally thesurface paper since what the finished laminate looks like depends mainlyon the surface paper. A topmost “overlay” sheet that is substantiallytransparent when cured may, however, be placed over the decorativesheet, for example, to give depth of appearance and wear resistance tothe finished laminate.

In a laminate where the surface paper has light-hued solid colors, anextra sheet of fine, white paper may be placed beneath the printedsurface sheet to prevent the amber-colored phenolic filler sheet frominterfering with the lighter surface color.

The texture of the laminate surface is determined by textured paperand/or a plate that is inserted with the buildup into the press.Typically, steel plates are used, with a highly polished plate producinga glossy finish, and an etched textured plate producing a matte finish.

The finished buildups are sent to a press, with each buildup (a pair oflaminates) is separated from the next by the above-mentioned steelplate. In the press, pressure is applied to the buildups by hydraulicrams or the like. Low and high pressure methods are used to make paperlaminates. Typically, at least 800 psi, and sometimes as much as 1,500psi pressure is applied, while the temperature is raised to more than250° F. by passing superheated water or steam through jacketing builtinto the press. The buildup is maintained under these temperature andpressure conditions for a time (typically about one hour) required forthe resins in the resin-impregnated papers to re-liquefy, flow and cure,bonding the stack together into a single sheet of finished, decorativelaminate.

Once removed from the press, the laminate sheets are separated andtrimmed to the desired finished size. Typically the reverse side of thelaminate is also roughened (such as by sanding) to provide a goodadhesive surface for bonding to one or more substrates such as plywood,hardboard, particle board, composites and the like. The need for andchoice of substrate and adhesive will depend on the desired end use ofthe laminate, as is recognized by one of ordinary skill in the relevantart.

The examples which follow, description of illustrative and typicalembodiments of the present disclosure are not intended to limit thescope of the disclosure. Various modifications, alternativeconstructions and equivalents may be employed without departing from thetrue spirit and scope of the appended claims.

EXAMPLES

Isoelectric Point Characterization Using the ZetaProbe (ColloidalDynamics).

A 4% solids slurry of the pigment was placed into the analysis cup. Theelectrokinetic sonic amplitude (ESA) probe and pH probe were submergedinto the agitated pigment suspension. Subsequent titration of thestirred suspension was accomplished using 2 N KOH as base and 2 N HNO₃as acid titrants. Machine parameters were chosen so that theacid-bearing leg was titrated down to pH 4 and the base-bearing leg wastitrated up to pH 9. The zeta potential was determined from the particledynamic mobility spectrum which was measured using the ESA techniquedescribed by O'Brian, et. al*. The pigment isoelectric point wastypically determined by interpolating where the zeta potential equalszero along the pH/zeta potential curve. *O'Brien R. W., Cannon D. W.,Rowlands W. N. J. Colloid Interface Sci. 173, 406-418 (1995).O'Brien R.W., Jones A., Rowlands W. N. Colloids and Surfaces A 218, 89-101 (2003).

Example 1

200 g. of a 30% (w/w) slurry of an amorphous alumina coated titaniumdioxide pigment (DuPont R-796) is charged into a jacketed 250 mL beakerand heated to 55° C. The slurry is stirred throughout the course ofsurface treatment using a propeller blade attached to an overheadstirrer. The pH of this slurry measures 5.5 at 55° C. 1.5 g. of a 43%sodium aluminate sol (24% Al₂O₃ content, about 1% Al₂O₃ based on pigmentweight) is charged into a 5 cc syringe. The sol is added at a rate of0.15 mL/min so that time for complete addition occurs within 10 min. ThepH is allowed to rise to 10, at which pH simultaneous addition of 20%HCl solution is commenced to maintain a pH of 10. After aluminateaddition is complete, 0.6 g. (7 mmol %) of3-(2-aminoethyl)-2,4-pentanedione is added to the stirred slurry. pH isadjusted to 10 and held for 30 min. After this period the pH isdecreased to 5.5 by further addition of 20% HCl and held at pH 5.5 for30 min. The slurry is vacuum filtered through a Buchner funnel fittedwith a Whatman #2 paper. The resulting cake is washed with 4×100 mL ofdeionized water, transferred onto a Petri dish, and dried at 110° C. for16 hrs. The dried cake is ground with a mortar and pestle. A 10% solidsslurry of this pigment is expected to give a pH of 6.5. A 4% solidsslurry of this pigment is expected to give an IEP (ZetaProbe) of 8.9. Asa comparative example, the starting R-796 pigment alone gave an IEP of6.9.

Example 2

200 g. of a 30% (w/w) slurry of an amorphous alumina coated titaniumdioxide pigment (DuPont R-796) is charged into a jacketed 250 mL beakerand heated to 55° C. The slurry is stirred using a propeller bladeattached to an overhead stirrer. 1.5 g. of a 43% sodium aluminate sol(24% Al₂O₃ content, about 1% Al₂O₃ based on pigment weight) is chargedinto a 5 cc syringe. The sol is added at a rate so that addition occurswithin 10 min. pH is allowed to rise to 10 and simultaneous addition of20% HCl solution is commenced to maintain a pH of 10. After aluminateaddition is completed, 3.0 g. (5 mmol %) of the Jeffamine® ED-900 adductof 3-oxo-butanamide is added to the stirred slurry. pH is adjusted to 10and held for 30 min. After this period the pH is decreased to 5.5 byfurther addition of 20% HCl and held at pH 5.5 for 30 min. The slurry isfiltered, washed, dried and ground as described in Example 1. A 10%solids slurry of this pigment is expected to give a pH of 6.5. A 4%solids slurry of this pigment is expected to give an IEP (ZetaProbe) of8.9.

Example 3

3330 g. of a 30% (w/w) solids R-796 slurry (i.e. enough to yield about 1Kg. dried pigment) is charged into a 5 L stainless steel pail and heatedto 55° C. on a hot plate. The slurry is stirred throughout using apropeller blade attached to an overhead stirrer. 20.0 g. of a 43% sodiumaluminate sol (24% Al₂O₃ content) is charged into a 20 cc syringe. Thesol is added at a rate so that addition is completed within 10 min. ThepH is allowed to rise to 10 and maintained at pH of 10 with simultaneousaddition of 20% HCl solution. After aluminate addition is completed,7.25 g. (5 mmol %) of N-(2-aminoethyl)-3-oxo-butanamide is added to thestirred slurry. The pH is adjusted to 10 and held for 30 min. After thisperiod, the pH is decreased to 5.5 by further addition of 20% HCl andheld for 30 min. The slurry is vacuum filtered through a large Buchnerfunnel fitted with Whatman #2 paper. The resulting cake is washed withdeionized water until the conductivity of the filtrate drops to <0.2mS/cm. The wet cake is transferred into an aluminum pan and dried at110° C. for 16 hrs. The dried cake is ground and sifted through a 325mesh screen. Final grinding of this material is accomplished in a steamjet mill. A 10% solids slurry of this pigment is expected to give a pHof 6.5. A 4% solids slurry of this pigment is expected to give an IEP(ZetaProbe) of 8.9.

What is claimed is:
 1. A self-dispersing pigment having an isoelectricpoint of at least about 8, comprising an inorganic particle treatedsequentially by (a) hydrolyzing an aluminum compound or basic aluminateto deposit a hydrous alumina surface; and (b) adding a dual-functionalcompound comprising i. an anchoring group that attaches thedual-functional compound to the pigment surface selected from acarboxylic acid functional group, a di-carboxylic acid group, anoxoanion functional group, a 1,3-diketone, 3-ketoamide, derivative of1,3-diketone, or derivative of 3-ketoamide, and i. ii a basic aminegroup comprising a primary, secondary or tertiary amine, and ii. atethering group that chemically connects the anchoring group to thebasic amine group wherein the tethering group comprises an alkyl chainof 1-8 carbon atoms; a carbon atom, an oxygen atom, a nitrogen atom, aphosphorus atom, a sulfur atom; or a polyetheramine comprisingpoly(oxyethylene) or poly(oxypropylene), or mixtures thereof; wherebythe weight average molecular weight of the polyetheramine tether isabout 220 to about
 2000. 2. The self-dispersing pigment of claim 1wherein inorganic particle is ZnO, TiO₂, SrTiO₃, BaSO₄, PbCO₃, BaTiO3,Ce₂O₃, Al₂O₃, CaCO₃ or ZrO₂.
 3. The self-dispersing pigment of claim 2wherein the inorganic particle is a titanium dioxide pigment having asurface area of at least about 10 m²/g.
 4. The self-dispersing pigmentof claim 1 wherein the anchoring group is a carboxylic acid functionalgroup that comprises acetate or salts thereof or a di-carboxylic acidgroup that comprises malonate, succinate, glutarate, adipate or saltsthereof.
 5. The self-dispersing pigment of claim 1 wherein the anchoringgroup is a 1,3-diketone or derivative of 1,3-diketone selected from2,4-pentanedione, 3-(2-aminoethyl)-2,4-pentanedione, or a derivative of2,4-pentanedione substituted at C-3 with ammine, an amine-containingfunctional group or salts thereof.
 6. The self-dispersing pigment ofclaim 1 wherein the anchoring group is an oxoanion functional groupselected from a substituted phosphate, phosphonate, sulfate, orsulfonate.
 7. The self-dispersing pigment of claim 3 wherein the basicamine comprises ammine; an N-alkyl amine of 1 to 8 carbon atoms; anN-cycloalkyl amine of 3 to 6 carbon atoms; an N,N-dialkyl amine of 2 to16 carbon atoms; N,N-dicycloalkyl amine of 6 to 12 carbon atoms; ormixtures of both alkyl and cycloalkyl substituents.
 8. Theself-dispersing pigment of claim 3 wherein the dual functional compoundcomprises alpha-amino acids selected from the group consisting oflysine, argenine, aspartic acid and salts thereof or alpha-omegaaminoacids selected from the group consisting of beta-alanine,gamma-aminobutyric acid, epsilon-aminocaproic acid and salts thereof. 9.The self-dispersing pigment of claim 3 wherein the dual-functionalcompound comprises (i) an aminomalonate derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group; R′ and R″ are each individually selectedfrom hydrogen, alkyl, cycloalkyl, alkyl-aryl, alkenyl, cycloalkenyl,alkene, alkylene, arylene, alkylarylene, arylalkylene or cycloalkylene;R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene;and n=0-50; (ii) an aminosuccinate derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group; R′ and R″ are each individually selectedfrom hydrogen, alkyl, cycloalkyl, alkyl-aryl, alkenyl, cycloalkenyl,alkene, alkylene, arylene, alkylarylene, arylalkylene or cycloalkylene;R₁ and R₂ are each individually selected from hydrogen, alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkene, alkylene, or cycloalkylene;and n=0-50; (iii) a 2,4-pentanedione derivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group; R₁ and R₂ are each individually selectedfrom hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkene,alkylene, and cycloalkylene; and n=0-50; or (iv) a 3-ketobutanamidederivative having the structure:

wherein X is a tethering group that chemically connects the anchoringgroup to the basic amine group; R₁ and R₂ are each individually selectedfrom hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkene,alkylene, and cycloalkylene.
 10. The self-dispersing pigment of claim 9wherein the tethering group “X” comprises: (a) an alkyl chain of 1-8carbon atoms; (b) a polyether chain comprising poly(oxyethylene) orpoly(oxypropylene), or mixtures thereof whereby the weight averagemolecular weight of the tethering group is about 220 to about 2000; or(c) polyetheramine co-polymers comprising both oxoethylene andoxopropylene monomers.
 11. The self-dispersing pigment of claim 9wherein R′ and R″ are hydrogen, methyl or ethyl and R₁ and R₂ arehydrogen, methyl, ethyl or propyl.
 12. The self-dispersing pigment ofclaim 9 wherein the dual-functional compound is an aminomalonatederivative selected from methyl ester of 2-(2-aminoethyl)malonic acid oran ethyl ester of 2-(2-aminoethyl)malonic acid or2-(2-aminoethyl)dimethylmalonate.
 13. The self-dispersing pigment ofclaim 9 wherein the dual-functional compound is an aminosuccinatederivative selected from methyl ester of N-substituted aspartic acid, anethyl ester of N-substituted aspartic acid or N-(2-aminoethyl)asparticacid.
 14. The self-dispersing pigment of claim 9 wherein thedual-functional compound is a 3-ketobutanamide (amidoacetate) derivativeselected from an ethylenediamine amide, a diethylenetriamine amide orN-(2-aminoethyl)-3-oxo-butanamide.
 15. The self-dispersing pigment ofclaim 3 wherein the aluminum compound is made from the salts comprisingaluminium chloride, aluminum sulfate, or aluminum nitrate or mixturesthereof or a basic aluminate from sources comprising sodium or potassiumaluminate.
 16. The self-dispersing pigment of claim 1 further comprisingat least one oxide treatment comprising aluminum oxide, silicon dioxide,zirconium oxide, cerium oxide, aluminosilicate or aluminophosphate. 17.The self-dispersing pigment of claim 3 wherein the titanium dioxidepigment comprises first an oxide layer comprising at least about 4%Al₂O₃ and at least about 1.5% P₂O₅, and a second layer comprising atleast about 3% Al₂O₃ and about 2 mmole % to about 10 mmole % of the dualfunctional compound, based on the total weight of the treated pigment.